Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type claw pairs; AISM ridged.”
Isohypsibioidea from Bertolani et al. 2014: “Double claws asymmetrical with respect to the median plane of the leg (2121), normally with similar shape and size on each leg; double claws of the Isohypsibius type (secondary branch of the external claw inserted perpendicularly on the claw basal tract), or reduced from it: Hexapodibius type (very short, without common basal tract, with a base as large as the sum of the primary and secondary branch widths, and with an evident suture between primary and secondary branch); Haplomacrobiotus type (one branch only); completely absent (Apodibius). Buccal tube completely rigid (apart Paradiphascon; see below) and often relatively large, without (Dastychius, Eremobiotus, Halobiotus, Isohypsibius, Paradiphascon, Pseudobiotus, Thulinius) or with (Apodibius, Doryphoribius, Haplomacrobiotus, Haplohexapodibius, Hexapodibius, Parhexapodibius) ventral lamina. Eggs with smooth shell laid within the exuvium.”
Hexapodibiidae from Cesari et al. 2016: “Double claws asymmetrical with respect to the median plane of the leg (2121), or with only the mainbranch, with the secondary branch being reduced or sometimes absent on some legs. Claws of Hexapodibius type very short and without a common basal tract, with a base as large as the sum of primary and secondary branch widths, and with an evident suture between the primary and the secondary branch; claws of Haplomacrobiotus type with one branch only, eventually with small spurs on the fourth pair of legs. Lunules and other cuticular thickenings absent on the legs in the known species. Peribuccal lobes and peribuccal papulae present. Buccal–pharyngeal apparatus of the Hexapodibius type (according to Pilato & Binda, 2010) with a completely rigid buccal tube and with a ventral lamina; pharyngeal apophyses and placoids present in the known species. Eggs with smooth shells, laid within the exuvia”
Genus description from Pilato & Beasley 1987: “hind legs reduced to short stumps lacking claws. First three pairs of legs with two single claws. Bucco-pharyngeal apparatus with the buccal tube provided with the ventral strengthening bar. Mouth without peribuccal lamellae, provided with 6 peribuccal papulae and 6 peribuccal lobes. Pharyngeal bulb provided with apophyses and placoids.”
Citations:
Bertolani R, Guidetti R, Marchioro T, Altiero T, Rebecchi L, Cesari M. 2014. Phyloeny of Eutardigrada: New molecular data and their morphological support lead to the identification of new evolutionary lineages. Molecular Phylogenetics and Evolution. 76: 110-126.
Cesari M, Vecchi M, Palmer A, Bertolani R, Pilato G, Rebecchi L, Guidetti R. 2016. What if the claws are reduced? Morphological and molecular phylogenetic relationships of the genus Haplomacrobiotus May, 1948 (Eutardigrada, Parachela). Zoological Journal of the Linnean Society. 178: 819-827.
Marley NJ, McInnes SJ, Sands CJ. 2011. Phylum Tardigrada: A re-evaluation of the Parachela. Zootaxa. 2819: 51-64.
Pilato G, Beasley CW. 1987. Haplohexapodibius seductor n. gen. n. sp. (Eutardigrada Calohypsibiidae) with remarks on the systematic position of the new genus. Animalia. 14: 65-71.
